The present invention relates to a defect testing apparatus and a defect testing method for inspecting a state of generation of defects such as foreign particles in a fabrication process such as a semiconductor fabrication process, a liquid-crystal-display fabrication process and a print-board fabrication process wherein a defect such as a foreign particle generated in a process to create a pattern on a substrate to produce an object is detected and analyzed in order to determine a countermeasure.
In the conventional semiconductor fabrication method, a foreign particle existing on a semiconductor substrate also known as a wafer causes a defect such as poor insulation of a wire or a short circuit. Furthermore, in the case of a miniaturized semiconductor device, an infinitesimal foreign particle existing in a semiconductor substrate results in poor insulation of a capacitor or destruction of typically a gate oxide film. These foreign particles are introduced to get mixed with a semiconductor material in a variety of states due to a variety of causes. For example, a foreign particle is generated by a movable part of a transportation apparatus or a human body. A foreign particle can also be generated as a result of a chemical reaction in processing equipment using a process gas or mixed with chemicals or a raw material.
Likewise, if a foreign particle is introduced to get mixed with a pattern, causing some defects in a process to fabricate a liquid-crystal display device, the resulting display device is not usable. The process to fabricate a print board is in the same situation. That is to say, a mixed foreign particle causes a poor connection and a short circuit in a pattern.
One technique for detecting a foreign particle on a semiconductor substrate of this type is disclosed in Japanese Patent Laid-open No. Sho 62-89336 and referred to hereafter as publication 1. According to this prior art, a laser beam is radiated to a semiconductor substrate. If a foreign particle is stuck to the semiconductor substrate, the foreign particle will generate scattered beams which can then be detected and compared with a result of inspection for a semiconductor substrate of the same type inspected immediately before. In this way, a difference in inspection result can be detected and used to eliminate a pattern defect. As a result, a foreign particle and a defect can be detected with a high degree of sensitivity and a high degree of reliability. Another publication referred to hereafter as publication 2 is disclosed in Japanese Patent Laid-open No. Sho 63-135848. According to this publication, a laser beam is radiated to a semiconductor substrate. If a foreign particle is stuck to the semiconductor substrate, the foreign particle will generate scattered beams which can then be detected. A detected beam generated by a foreign particle is analyzed by using an analysis technique such as laser photo luminescence or a secondary X-ray analysis (XMR).
In addition, as a technology for detecting a foreign particle, there is also known a technique whereby a coherent beam is radiated to a wafer, and the beam reflected by repetitive patterns on the wafer is removed by a spatial filter to emphasize light components generated by a foreign particle or a defect which does not exhibit repetitiveness. In this way, a foreign particle or a defect can be detected.
A technology disclosed in Japanese Patent Laid-open No. Hei 1-117024 is referred to hereafter as publication 3. According to this publication, in a foreign particle inspecting apparatus, a beam is radiated to a circuit pattern on a wafer in a direction forming an angle of 45 degrees with respect to a group of main straight lines of the circuit pattern and a 0th-order diffracted beam from the group of main straight lines is introduced into the aperture of an objective lens. The disclosure also includes a description which states that, according to publication 3, a beam from any group of straight lines other than the group of main straight lines is shielded by a spatial filter.
In addition, other publications related to apparatuses and methods for detecting defects such as foreign particles are disclosed in Japanese Patent Laid-open No. Hei 1-250847, Japanese Patent Laid-open No. Hei 6-258239, Japanese Patent Laid-open No. Hei 6-324003, Japanese Patent Laid-open No. Hei 8-210989 and Japanese Patent Laid-open No. Hei 8-271437 and referred to as publications 4, 5, 6 7 and 8 respectively.
With the teachings of publications 1 to 8 mentioned above, however, it is impossible to detect a defect such as an infinitesimal foreign particle on a substrate, on which repetitive patterns coexist with non-repetitive patterns, at a high speed, with ease and with a high degree of sensitivity.
To put it in detail, the teachings of publications 1 to 8 have a problem of a substantially reduced sensitivity (increased minimum dimensions of a detected foreign particle) in the case of a part of the substrate other than the repetitive portion such as memory cells.
In addition, the teachings of publications 1 to 8 also have a problem of a substantially reduced sensitivity in the case of an oxide film which passes a radiation beam.
Moreover, the teachings of publications 1 to 8 also have a problem of inability to detect a defect such as an infinitesimal foreign particle.
Furthermore, in the case of the teachings of publications 1 to 8, a mass-production build-up line or a pilot line and a mass-production line of a semiconductor production process are not distinguished from each other. That is to say, inspection equipment used in the mass-production build-up work is also used in a mass-production line without change in spite of the fact that it is necessary to detect generation of a foreign particle on the mass-production line early, to efficiently determine a countermeasure for the detected foreign particle.
At any rate, the conventional defect inspecting apparatus is large in size and has such a configuration that the apparatus must be installed independently. For this reason, in order to inspect a foreign particle and a defect, it is necessary to transport a semiconductor substrate, a liquid-crystal-display substrate or a print substrate which has been processed along the mass-production line to a place at which the defect inspecting apparatus is installed. That is to say, it takes time to transport the substrate and to inspect the substrate for a foreign particle and a defect. As a result, complete inspection is difficult. In addition, it is hard to carry out such sampling inspection at a sufficiently high frequency.
Further, a defect inspecting apparatus with such a configuration requires an operator.
It is thus an object of the present invention addressing the problems described above to provide a defect inspecting apparatus and a defect inspection method capable of inspecting a defect such as an infinitesimal foreign particle on an inspected substrate containing repetitive patterns, non-repetitive patterns and non-patterns which coexist with each other at a high speed and with a high degree of precision.
It is another object of the present invention to provide a defect inspecting apparatus and a defect inspection method which allow a high-efficiency substrate fabrication line to be constructed by implementation of complete inspection and sampling inspection at a sufficiently high frequency.
It is still another object of the present invention to provide a defect inspecting apparatus and a defect inspection method which are capable of inspecting also a defect such as an extremely infinitesimal foreign particle having a size of the order of 0.1 xcexcm or smaller at a high speed and with a high degree of sensitivity by effectively utilizing the light quantity of a Gaussian beam generated by an ordinary inexpensive light source such as a laser-beam source.
It is a further object of the present invention to provide a defect inspecting apparatus and a defect inspection method which are capable of inspecting also a defect such as an extremely infinitesimal foreign particle having a size of the order of 0.1 xcexcm or smaller at a high speed and with a high degree of sensitivity by effectively utilizing the light quantity of a Gaussian beam generated by typically a laser-beam source and by resolving a problem of a lack of illumination at regions surrounding an area on a substrate being inspected due to a decrease in MTF at locations separated away from an optical axis in a detection optical system.
It is a still further object of the present invention to provide a defect inspecting apparatus capable of inspecting a defect such as a real foreign particle by setting the level of a threshold value at a proper degree of sensitivity without substantially increasing the amount of generated false information wherein the threshold value is used as a criterion as to whether or not a defect exists in a variety of circuit-pattern areas in the device structure laid out on a substrate being inspected.
It is a still further object of the present invention to provide a defect inspecting apparatus capable of inspecting a defect such as a foreign particle with a specified size to be detected by setting the level of a threshold value used as a criterion as to whether or not a defect exists for the size of the defect to be detected in a variety of circuit-pattern areas in the device structure laid out on a substrate being inspected.
It is a still further object of the present invention to provide a defect inspecting apparatus capable of inspecting a defect such as a foreign particle by allowing the size of the defect existing in a variety of circuit-pattern areas in the device structure laid out on a substrate being inspected to be inferred.
It is a still further object of the present invention to provide a semiconductor-substrate fabricating method for fabricating a semiconductor substrate at a high efficiency and, hence, at a high yield.
In order to achieve the objects described above, the present invention provides a defect inspecting apparatus and a defect inspection method adopted by the defect inspecting apparatus comprising: a stage for mounting and moving an inspected substrate with a circuit pattern created thereon; an illumination optical system for illuminating the substrate by forming a beam radiated by a light source into a slit-shaped beam and directing the beam toward the substrate being inspected at a predetermined gradient of (xcfx80/2xe2x88x92xcex11) with respect to the direction of a line normal to the substrate and a predetermined gradient of "PHgr"1 with respect to a group of main straight lines of the circuit pattern on the surface of the substrate wherein the longitudinal direction is almost perpendicular to a direction of the y axis of the movement of the stage; a detection optical system including an image sensor for receiving scattered beams reflected by a defect such as a foreign particle existing on the inspected substrate illuminated by the slit-shaped beam radiated by the illumination optical system and for converting the scattered beams into a detection signal representing a result of detection of the defect; and an image-signal processing unit for extracting a signal showing the defect such as a foreign particle on the basis of the detection signal output by the image sensor employed in the detection optical system.
In addition, in order to achieve the objects described above, the present invention also provides a defect inspecting apparatus and a defect inspection method adopted by the defect inspecting apparatus comprising: a stage for mounting and moving an inspected substrate with circuit patterns created thereon; an illumination optical system for illuminating the substrate by forming a beam radiated by a light source into a slit-shaped beam and directing the beam toward the substrate being inspected at a predetermined gradient of (xcfx80/2xe2x88x92xcex11) with respect to the direction of a line normal to the substrate and a predetermined gradient of "PHgr"1 with respect to a group of main straight lines of the circuit pattern on the surface of the substrate wherein the longitudinal direction is almost perpendicular to a direction of the y axis of the movement of the stage; a detection optical system including an image sensor for receiving scattered beams reflected by a defect such as a foreign particle existing on the inspected substrate illuminated by the slit-shaped beam radiated by the illumination optical system and for converting the scattered beams into a detection signal representing a result of detection of the defect; and an image processing unit having: a criterion setting means which calculates a variation of the detection signal output by the image sensor of the detection optical system to represent a variation of a scattered beam reflected by areas on the surface of the substrate in which the naturally identical circuit patterns are created or regions in close proximity to the areas and which sets a criterion (threshold value) based on the calculated variation; and a signal extracting means which extracts a signal showing the defect such as a foreign particle from the detection signal output by the image sensor employed in the detection optical system on the basis of the criterion set by the criterion setting means.
Furthermore, the present invention also provides a defect inspecting apparatus and a defect inspection method adopted by the defect inspecting apparatus comprising: a stage unit for mounting and moving an inspected substrate with a circuit pattern created thereon; an illumination optical system for illuminating the substrate by forming a beam radiated by a light source into a slit-shaped beam and directing the beam toward the substrate being inspected at a predetermined gradient with respect to the direction of a line normal to the substrate and a predetermined gradient with respect to a group of main straight lines of the circuit pattern on the surface of the substrate wherein the longitudinal direction is almost perpendicular to a y direction of the movement of the stage; a detection optical system including an image sensor for receiving scattered beams reflected by a defect such as a foreign particle existing on the inspected substrate illuminated by the slit-shaped beam radiated by the illumination optical system and for converting the scattered beams into a detection signal representing a result of detection of the defect; and an image-signal processing unit for extracting a signal showing the defect such as a foreign particle from the detection signal output by the image sensor employed in the detection optical system on the basis of a criterion (threshold value) set for each of a variety of areas composing the circuit pattern.
Moreover, in the defect inspecting apparatuses and the defect inspection methods provided by the present invention, the predetermined gradient of "PHgr"1 of the slit-shaped beams with respect to a group of main straight lines of the circuit pattern on the surface of the substrate is about 45 degrees.
Further, in the defect inspecting apparatuses and the defect inspection methods provided by the present invention, the optical axis of the detection optical system is substantially perpendicular to the substrate being inspected.
In addition, in the defect inspecting apparatuses and the defect inspection methods provided by the present invention, the optical axis of the detection optical system is inclined with respect to the line normal to the substrate being inspected.
Furthermore, in the defect inspecting apparatus provided by the present invention, the light source employed in the illumination optical system is a laser-beam source.
Moreover, in the defect inspecting apparatus provided by the present invention, the illumination optical system has an optical element of a shape resembling a cone for generating a converged light.
Further, in the defect inspecting apparatus provided by the present invention, the illumination optical system is provided with an optical system for radiating a white light in a direction inclined with respect to a normal line to a substrate being inspected.
In addition, in the defect inspecting apparatus provided by the present invention, the illumination optical system is provided with a space filter.
Furthermore, in the defect inspecting apparatus provided by the present invention, the image sensor employed in the detection optical system is a TDI (Time Delay Integration) image sensor.
Moreover, the present invention provides a defect inspecting apparatus comprising: an illumination optical system having an optical element of a shape resembling a cone for radiating an illumination light beam in a direction at a predetermined gradient with respect to a line normal to the surface of an object of inspection and for converging the illumination light beam in at least one direction on the surface of the object of inspection; a detection optical system including an image sensor which receives a light reflected by the object of inspection and converts the received light into a detection signal; and an image-signal processing unit for processing the detection signal output by the detection optical system.
Further, the detection optical system employed in the defect inspecting apparatus provided by the present invention has: a beam splitting optical system for splitting a light beam reflected by the object of inspection into reflected beams with one of the reflected beams having an intensity of about 1/100 of that of another; and a plurality of image sensors for receiving each of the reflected beams split by the beam splitting optical system.
In addition, the present invention provides a defect inspecting apparatus comprising: an illumination optical system for radiating an illumination light to a surface of an object of inspection on which a plurality of circuit patterns with substantially identical shapes are laid out; a detection optical system including an image sensor for receiving a light reflected by the object of inspection and for converting the received light into a detected image signal; and an image-signal processing unit for processing the detected image signal and being provided with: a criterion setting means which calculates a variation of an image signal among pixels which correspond to the circuit patterns with identical shapes or pixels in close proximity thereto on the basis of the image signal detected by the detection optical system and which sets a threshold value to serve as a criterion as to whether or not a defect such as a foreign particle exists on the basis of the calculated variation of the image signal; and a judgment means which forms a judgment as to whether or not a defect exists from the image signal detected by the detection optical system on the basis of the criterion set by the criterion setting means.
Furthermore, the present invention provides a defect inspecting apparatus comprising: an illumination optical system for radiating an illumination light to a surface of an object of inspection on which a plurality of patterns with substantially identical shapes are laid out; a detection optical system including an image sensor for receiving a light reflected by the object of inspection and for converting the received light into a detected image signal; and an image-signal processing unit for processing the detected image signal and being provided with: a difference computing means which computes differences in image signal among pixels corresponding to the patterns having identical shapes on the basis of an image signal detected by the detection optical system; a criterion setting means which calculates a variation of the differences computed by the difference computing means at a plurality of for pixels adjacent to pixels used for forming a judgment as to whether or not a defect such as a foreign particle exists and which sets a criterion of the level of a pixel signal used for determining whether or not the defect such as the foreign particle exists on the basis of the calculated variation; and a judgment means which forms a judgment as to whether or not the defect exists from the image signal detected by the detection optical system on the basis of the criterion set by the criterion setting means.
Moreover, in the defect inspecting apparatus provided by the present invention, the image-signal processing unit has an output means which outputs pieces of a result of defect inspection produced by the judgment means and data representing the criterion set by the criterion setting means.
Further, the present invention provides a defect inspecting apparatus comprising: an illumination optical system for radiating an illumination light to a surface of an object of inspection on which a plurality of patterns with substantially identical shapes are laid out; a detection optical system including an image sensor for receiving a light reflected by the object of inspection and for converting the received light into a detected image signal; and an image-signal processing unit having: a judgment means which forms a judgment as to whether or not a defect exists by comparison of the image signal output by the detection optical system with a criterion; and a display means which displays map information or images on the patterns having identical shapes to be used as the criterion by the judgment means, or which displays relations between criteria (or sensitivities) and indicators of inspection area for them, or which displays sensitivity information on circuit patterns having identical shapes corresponding to criteria.
In addition, the image-signal processing unit employed in the defect inspecting apparatus provided by the present invention has an area priority mode, a standard mode and a sensitivity priority mode as condition specifying modes.
Furthermore, the present invention provides a defect inspecting apparatus comprising: an illumination optical system for radiating an illumination light to a surface of an object of inspection on which a plurality of patterns with substantially identical shapes are laid out; a detection optical system including an image sensor for receiving a light reflected by the object of inspection and for converting the received light into a detected image signal; and an image-signal processing unit for processing the detected image signal and being provided with: a criterion setting means which sets a criterion by varying the criterion in accordance with a state of an underlying layer in the patterns with identical shapes; and a judgment means which forms a judgment as to whether or not a defect exists by comparison of the image signal output by the detection optical system with the criterion set by the criterion setting means.
Moreover, the present invention provides a defect inspecting apparatus comprising: an illumination optical system for radiating an illumination light to a surface of an object of inspection on which a plurality of patterns with substantially identical shapes are laid out; a detection optical system including an image sensor for receiving a light reflected by the object of inspection and for converting the received light into a detected image signal; and an image-signal processing unit for processing the detected image signal output by the detection optical system and being provided with: a size specifying means which specifies a size of a defect; a criterion setting means which sets a criterion by varying the criterion in accordance with the defect size specified by the size specifying means; and a judgment means which forms a judgment as to whether or not a defect exists by comparison of the image signal output by the detection optical system with the criterion set by the criterion setting means.
Further, the present invention provides a defect inspecting apparatus comprising: an illumination optical system for radiating an illumination light to a surface of an object of inspection on which a plurality of patterns with substantially identical shapes are laid out; a detection optical system including an image sensor for receiving a light reflected by the object of inspection and for converting the received light into a detected image signal; and an image-signal processing unit for processing the detected image signal output by the detection optical system and being provided with: a size specifying means which specifies a size of a defect; and a control means which controls the power of the illumination light radiated by the illumination optical system in accordance with the defect size specified by the size specifying means.
In addition, the present invention provides a defect inspecting apparatus comprising: an image-pickup optical system having: an illumination optical subsystem for radiating an illumination light to a surface of an object of inspection mounted on a stage with the object having a plurality of patterns having substantially identical shapes laid out on the object of inspection; and a detection optical subsystem including an image sensor for receiving a light reflected by the object of inspection and for converting the received light into a detected image signal; an image-signal processing unit including a judgment means which forms a judgment as to whether or not a defect exists by comparison of the image signal output by the detection optical sub system employed in the image-pickup optical system with a criterion; and an optical observation microscope provided along with the image-pickup optical system and used for observation of an optical object on the object of inspection.
Furthermore, in the defect inspecting apparatus provided by the present invention, the optical observation microscope is implemented by an ultraviolet-ray optical observation microscope.
Moreover, the present invention provides a defect inspecting apparatus comprising: an illumination optical system for radiating an illumination light to a surface of an object of inspection; a detection optical system including a photo-electrical conversion means which receives a light reflected by the object of inspection and converts the received light into a detected signal; and an image-signal processing unit including a means which detects a defect by processing the signal detected by the detection optical system and outputs a result of the defect detection including pattern information indicating existence of a defect.
Further, in the defect inspecting apparatus provided by the present invention, the pattern information output by the means employed in the image-signal processing unit is information obtained from design data of patterns.
In addition, the present invention provides a defect inspecting apparatus comprising: an illumination optical system for radiating an illumination light to a surface of an object of inspection; a detection optical system including a photo-electrical conversion means which receives a light reflected by the object of inspection and converts the received light into a detected signal; and an image-signal processing unit including a means which extracts a signal level of a defect by processing the signal detected by the detection optical system, and which corrects the extracted defect signal level so as to make the signal level indicate the size of the defect, and which outputs the corrected defect signal level.
Furthermore, the means employed in the image-signal processing unit of the defect inspecting apparatus provided by the present invention corrects the signal level of the defect on the basis of the intensity of the illumination light or data representing the reflectance of the surface of a pattern.
Moreover, the illumination optical system employed in the defect inspecting apparatus provided by the present invention is configured so that a light source thereof radiates a slit-shaped beam to a detection area on a substrate serving as an object of inspection wherein the slit-shaped beam is formed into a slit-shaped Gaussian beam exhibiting a Gaussian illumination distribution having a standard deviation substantially equal to a distance from an optical axis of the detection area to a periphery.
Further, the illumination optical system employed in the defect inspecting apparatus provided by the present invention is configured to have a light source thereof radiate a slit-shaped beam to a detection area on a substrate serving as an object of inspection wherein the slit-shaped beam is formed into a slit-shaped Gaussian beam by properly adjusting a diameter or a major-axis length of the beam to a distance between peripheries having the center thereof coinciding with an optical axis of the detection area so that a ratio of an illumination at the peripheries of the detection area to an illumination at the center of the detection area has a value in the range 0.46 to 0.73.
In addition, in the defect inspecting apparatus provided by the present invention, the slit-shaped Gaussian beam radiated by the illumination optical system is a DUV (Deep Ultra-Violet) beam.
In the configurations described above, it is possible to detect a defect such as an infinitesimal foreign particle on an inspected substrate, on which repetitive patterns, non-repetitive patterns and non-patterns coexist with each other, at a high speed and with a high degree of precision.
In addition, in the configurations described above, by effectively utilizing the light quantity of a Gaussian beam radiated by an ordinary inexpensive light source such as a laser-beam source, it is possible to detect also a defect such as an infinitesimal foreign particle with a size of the order of 0.1 xcexcm or smaller at a high speed and with a high degree of sensitivity.
Furthermore, in the configurations described above, by effectively utilizing the light quantity of a Gaussian beam radiated by typically a laser-beam source, it is possible to detect also a defect such as an infinitesimal foreign particle with a size of the order of 0.1 xcexcm or smaller at a high speed and with a high degree of sensitivity by resolving a problem of a lack of illumination at regions surrounding an area on a substrate being inspected due to a decrease in MTF at locations separated away from an optical axis in a detection optical system.
Moreover, in the configurations described above, it is possible to detect a defect such as a real foreign particle by setting the level of a threshold value at a proper degree of sensitivity without substantially increasing the amount of generated false information wherein the threshold value is used as a criterion as to whether or not a defect exists in a variety of circuit-pattern areas in the device structure laid out on a substrate being inspected.
Further, in the configurations described above, it is possible to detect a defect such as a foreign particle with a size to be detected by setting the level of a threshold value used as a criterion as to whether or not a defect exists for the size of the defect to be detected in a variety of circuit-pattern areas in the device structure laid out on a substrate being inspected.
In addition, in the configurations described above, it is possible to detect a defect such as a foreign particle by allowing the size of the defect existing in a variety of circuit-pattern areas in the device structure laid out on a substrate being inspected to be inferred.
Furthermore, in the configurations described above, it is possible to construct a high-efficiency substrate fabrication line by implementation of complete inspection and sampling inspection at a sufficiently high frequency.